win32: emulate SIGPIPE

The code to check whether a write error is due to a broken pipe
can now either:

- return with error EPIPE;
- cause the process to exit with code 128+SIGPIPE.

The default is the latter but the behaviour can be changed by issuing
signal(SIGPIPE, SIG_IGN) and signal(SIGPIPE, SIG_DFL) calls.

No actual signal is involved so kill can't send SIGPIPE and handlers
other than SIG_IGN and SIG_DFL aren't supported.

This does, however, avoid unsightly 'broken pipe' errors from commands
like the example in GitHub issue #99:

  dd if=/dev/urandom | tr -dc _A-Z-a-z-0-9 | head -c${1:-32};echo;

1 files changed, 0 insertions, 2 deletions

diff --git a/archival/tar.c b/archival/tar.c
index 22ad0e0f2..7dd89a282 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -1122,9 +1122,7 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 
         if (opt & OPT_2COMMAND) {
                 putenv((char*)"TAR_FILETYPE=f");
-#ifdef SIGPIPE
                 signal(SIGPIPE, SIG_IGN);
-#endif
                 tar_handle->action_data = data_extract_to_command;
                 IF_FEATURE_TAR_TO_COMMAND(tar_handle->tar__to_command_shell = xstrdup(get_shell_name());)
         }